Transcript Document
Cancer, Diet & Phytochemicals Causes of Death in US, 2010 In 2010, a total of 2,468,435 deaths occurred in the United States. The first two leading causes of death, heart disease (597,689 deaths) and cancer (574,743), accounted for nearly 50% of all deaths.. Heart disease killed almost 300,000 women in 2010. Key Concepts: Cancer Cancer has many causes Diet is a factor that influences the development of some types of cancer Lifestyles and diets based on plant foods that include lean meats, fish, and low-fat dairy products regular physical activity, and normal levels of body fat reduce cancer risk Cancer is largely preventable, but there are no guarantees that an individual will not develop cancer What Is Cancer? Cancer, second leading cause of death in the U.S., is really some 200 diseases that cause the uncontrolled growth of abnormal cells (NIH director) Cells can begin to grow in any tissue, but lungs, colon, prostate, and breasts are the most common sites for cancer development Some forms of cancer are highly curable Estimated Cancer Deaths in the US in 2013 38,280 deaths from breast cancer Development of Cancer Cancer develops by processes not yet fully understood Cancer development is not linear - cancer can progress two steps forward and then take a step or two back Cancer begins when something goes wrong that modifies cell division Every minute, 10 million cells in the body divide Usually they divide the right way Phases At initiation something alters DNA in certain cells During promotion phase, cancer cells with altered DNA divide, producing large numbers of abnormal cells This phase takes place over 10 to 30 years Unless corrected by some means, abnormal cells continue to divide, leading to progression phase of cancer development Progression Phase Body loses control over abnormal cells, numbers increase rapidly Eventually cells become so numerous they erode normal functions where they are growing Now abnormal cells can migrate (metastasize) to other tissues and cause DNA damage and abnormal cell development in these tissues, too What Causes Cancer? 80-90% of all cancers are related to environmental factors, including – – – – smoking exposure to asbestos chemical pollutants radiation And diet-- a major environmental factor-may account for 40% of cancer risk Environmental Factors Rates of breast cancer are low in rural Asia When rural Asians immigrate to U.S., rates of breast cancer become same or higher than U.S. rate by third generation Rates of prostate cancer similarly increase as people move from countries with low-tohigh rates Dietary Factors Westernization of dietary intake and lifestyle increases the risk of many types of cancer Rates of breast cancer in Japanese and Eskimo women increase substantially as Westernized diets and lifestyles have become adopted Genetic Factors Some people have genetic susceptibility to certain cancers They develop cancer if regularly exposed to certain substances in the diet or environment Genetic factors account for 42% of risk for prostate cancer, 5 to 27% of risk for breast cancer, and 36% of risk for pancreatic cancer Cancer Preventable Cancer is a largely preventable disease Increasing rates of new cases of lung cancer took a turn for the better after 1992 and correspond to declines in rates of tobacco use for men Other changes in lifestyles and diets may lead to further declines in cancer rates … or to increases Cancer-promoting lifestyle DIET Red meats and saturated fat Includes charred and nitrate-cured meats Excessive alcohol Other Risk Factors Smoking Physical inactivity Excess body fat Eating to Beat the Odds Two thirds of people in U.S. do not develop cancer Improve your odds by – – – – – – not smoking Eating a low red-meat and saturated-fat diet being physically active drinking in moderation or not at all consuming plenty of fruits and vegetables daily maintaining a normal level of body fat No guarantees, but you help prevent cancer by a good diet and a healthy lifestyle The Latest: Red meat may raise young women’s breast cancer risk Compared with women who had one serving of red meat a week, those who ate 1.5 servings a day appeared to have a 22% higher risk of breast cancer. additional red meat seemed to increase the risk of breast cancer more. Harvard researchers drew from data on the health of 89,000 women aged 24 to 43, who were followed over a 20year period. June 2014 British Medical Journal. Fig. 22-1, p. 6 Grilled and Charred Meats Substances in beef, chicken, fish, and other meats become cancer promoting if heated to high temperatures High temperatures can be reached by broiling and grilling food Cancer-promoting substances are in charred portions of meat and fatty coating that forms on meat when fat drips into heat source and smokes But the problem is not just grilled meat… One European study tracked 478,000 men and women…. those who ate the most red meat (about 5 ounces a day or more) were a third more likely to develop colon cancer than those who ate the least red meat (less than an ounce a day on average). Consumption of chicken did not matter, and consumpton of fish reduced risk. Nitrate-Preserved Meats Cancer of stomach and liver related to regular consumption of hot dogs, lunch meats, bacon, pickled eggs, and vegetables preserved with nitrates Most cases of cancer from nitrate use in smoked, salted, and pickled foods now occur in China, the former Soviet Union, and Central and South America where such foods are very frequently eaten Recommendations for Protein Include plant sources of protein because plants also provide unsaturated fats Dried beans, soy products, nuts, and seeds provide vitamins, minerals, fiber, and more phytochemicals that help ward-off cancer progression Regular consumption of fish related to lower rates of cancer Poultry consumption doesn’t increase risk Limit beef to no more than two 4-oz servings a week Harvard Summary, 2012 Alcohol-Attributable Cancer Deaths Total cancer deaths 574,743 Alcohol consumption resulted in about 20,000 cancer deaths per year, 3.5% of all US cancer deaths. About 6,000 from breast cancer Heart disease killed almost 300,000 women in 2010. Body Fat and Cancer Central obesity increases the risk of cancer at several sites Central fat alters metabolism of hormones such as estrogen, testosterone, and insulin to promote growth of abnormal cells FOCUS: Phytochemicals Diets containing vegetables, fruits, whole grains, all rich in phytochemicals strongly associated with low rates of chronic heart disease and cancer Phytochemicals (aka phytonutrients) Chemical substances found in plants Thousands of phytochemicals in plants, and some foods contain hundreds Not essential, we do not develop a deficiency disease if we consume too little Many are antioxidants How Do They Work? Phytochemicals: -- Act as hormone-inhibitors to prevent initiation of cancer – – – – Antioxidants that prevent and repair damage due to oxidation block enzymes that promote cancer and other diseases modify absorption, production, or utilization of cholesterol decrease formation of blood clots Some plant pigments are powerful antioxidants – zeaxanthin, anthocyanin and lycopene are strong antioxidants – dark chocolate contains flavonoid antioxidants – some phytochemical antioxidants reduce plaque formation by preventing the oxidation of LDL Antioxidants May participate in cancer prevention by protecting cells from damage due to oxidation and by inhibiting the multiplication of abnormal cells Vitamin C, beta-carotene, vitamin E, and selenium are well-known antioxidants in vegetables and fruits Damage to DNA related to cancer initiation may be caused by exposure to oxidizing substances that disrupt molecules within DNA Antioxidants are able to repair damaged DNA Carotenoids Alpha, Beta, and Gamma carotenes Lycopenes, lutein, etc., etc. May protect against prostate cancer May protect against lung cancer Tomatoes, tomato sauce Watermelon, red grapefruit, guava Red peppers, chili peppers, green peppers Apricots Color Coding Cruciferous Vegetables Fig. 21-5, p. 5 Cruciferous Vegetables 3 cruciferous vegetable servings per week may reduce the risk of lung, bladder, and prostate cancer Broccoli Cabbage Collards, mustard, turnip greens, Bok choy, brussels sprouts, cauliflower Whole Grains and Cancer Whole grains have vitamins, minerals, fiber, unsaturated fatty acids, and those phytochemicals that work together in cancer prevention Effect on cancer risk is related to the combined action of these substances Advice: include three or more 100% whole grain products daily Phytochemicals Phytochemicals are heat and light stable, not easily destroyed by cooking or storage Many are excreted soon after ingestion, so intake of vegetables, legumes, nuts, fruits, and other food sources should be frequent Cooking vegetables or eating with fat/oil increases absorption of phytochemicals Characteristics Phytochemicals provide color and flavor and protect plants from insects, microbes, and oxidation due to exposure to sunlight and oxygen Some are components of a plant’s energy-making processes Some act as plant hormones Many are pigments, like anthocyanins & function as antioxidants Phytochemicals and Health Phytochemicals are associated with a reduced risk of developing: – heart disease – certain types of cancer (lung, breast, cervical, esophageal, stomach, and colon cancer) – age-related macular degeneration, cataracts – infectious diseases – Type 2 diabetes – Hypertension, stroke – and other disorders Evidence supports role for phytochemicals *Clinical studies to demonstrate cause-and-effect relationships have yet to be completed Phytochemicals in Groups There is no solid evidence that individual phytochemicals extracted from foods benefit health Absorption appears to depend on other phytochemicals and nutrients Most phytochemicals act together synergistically Optimal combinations are not yet known, so let foods provide them Broccoli: in just 1 cup Over 30 phytochemicals including Indol-3-carbinol (first cancer-protective phytochemical, discovered in 1970’s) 90% RDA for Vitamin A 200% RDA for Vitamin C 25% daily recommendation for fiber Fair amounts of niacin, pantothenic acid, folacin, iron, vitamin K, calcium, thiamin & phosphorus Fig. 21-2, p. 3 Dietary Risk Factors Foods contain vitamins and minerals, fiber and phytochemicals that protect the body against cancer Substances in plant foods appear to work synergistically to confer protection Attempts to prevent cancer by dosing with individual components of plants have not been successful Foods provide protection against cancer, but extracted phytochemical supplements do not Diets that prevent cancer are based on regular intake of an array of foods Extracts and Essences Dehydrated extracts of vegetables high in phytochemicals are available There is no evidence that these extracts benefit health “Broccoli Concentrate” contains one phytochemical from the cruciferous family Only so much will fit into a capsule, so it takes 100’s of pills to get same amount as one serving of broccoli! Supplements of phytochemicals are unsafe and ineffective Diet and Cancer Guidelines Dietary patterns and lifestyles to reduce risk of cancer are compatible with dietary recommendations to reduce the risk of heart disease Considered together, recommendations for cancer prevention and heart disease prevention can be transferred to dietary intake by proper selection of foods Benefits from diets high in plant foods Vegetables, fruits, whole grains, and other plant foods reduce: Heart disease Cancer Type 2 diabetes Infections Eye disease Premature aging and a number of other health problems The End Fig. 21-4, p. 5